In May 2012 I wrote an article on “The risk factors in knee pain”. In this article I discussed a study which showed the relevant risk factors in developing ANTERIOR knee pain, or otherwise known as Patello-Femoral Pain Syndrome (PFPS). You can read the article by clicking HERE.
In this study, one of the five risk factors that were found to be associated with PFPS, was “STRENGTH”, specifically that of the Quadriceps muscles which straighten your knee. Some of the advice then given was to strengthen your quadricep muscle through exercises such as squats and resisted knee extension.
Now, in a more recent study which examined the amount of strain placed on the Patello-femoral joint (knee-cap) during different exercises (squats and knee extension), researchers were able to conclude that there are “safe” ranges of motion during these exercises as well as “unsafe” ranges, which would either place a little or a lot of strain on the Patello-femoral joint.
What the above image demonstrates is that during a squat movement, the “safe” range of motion is between 0 and 45 degrees of knee bending, and the “unsafe” zone from 45 to 90 degrees of bend. So when performing a squat to strengthen the quadricep muscle in PFPS, ONLY GO HALF WAY DOWN!
However, when performing a seated knee extension exercise, the “safe zone” is from 45 to 90 degrees, and the “unsafe zone”, 0 to 45 degrees of bend. So when performing a resisted leg extension exercise, ONLY GO HALF WAY UP!
By training in the “safe” zones for both of these types of exercises, you can strengthen your quadriceps muscles and at the same time, avoid feeling knee pain. If you are already experiencing pain under your knee cap, always consult your Physio prior to starting these exercises. Once you can do these exercises pain free, your Physio will progress them accordingly.
Article by Powers et al, titled “Patellofemoral Joint Stress During Weight-Bearing and Non–Weight-Bearing Quadriceps Exercises,” J Orthop Sports Phys Ther 2014;44(5):320-327. Epub 27 March 2014.doi:10.2519/jospt.2014.4936
BY: Riccardo Vaccaro
Knee injuries, Lower Limb injuries